// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
// http://github.com/jskeet/dotnet-protobufs/
// Original C++/Java/Python code:
// http://code.google.com/p/protobuf/
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.IO;
using Google.ProtocolBuffers.DescriptorProtos;
using FileOptions = Google.ProtocolBuffers.DescriptorProtos.FileOptions;

namespace Google.ProtocolBuffers.Descriptors {
  /// <summary>
  /// Describes a .proto file, including everything defined within.
  /// IDescriptor is implemented such that the File property returns this descriptor,
  /// and the FullName is the same as the Name.
  /// </summary>
  public sealed class FileDescriptor : IDescriptor<FileDescriptorProto> {
    private FileDescriptorProto proto;
    private readonly IList<MessageDescriptor> messageTypes;
    private readonly IList<EnumDescriptor> enumTypes;
    private readonly IList<ServiceDescriptor> services;
    private readonly IList<FieldDescriptor> extensions;
    private readonly IList<FileDescriptor> dependencies;
    private readonly DescriptorPool pool;
    private CSharpFileOptions csharpFileOptions;
    private readonly object optionsLock = new object();

    private FileDescriptor(FileDescriptorProto proto, FileDescriptor[] dependencies, DescriptorPool pool) {
      this.pool = pool;
      this.proto = proto;
      this.dependencies = new ReadOnlyCollection<FileDescriptor>((FileDescriptor[]) dependencies.Clone());

      pool.AddPackage(Package, this);

      messageTypes = DescriptorUtil.ConvertAndMakeReadOnly(proto.MessageTypeList,
                                                           (message, index) =>
                                                           new MessageDescriptor(message, this, null, index));

      enumTypes = DescriptorUtil.ConvertAndMakeReadOnly(proto.EnumTypeList,
                                                        (enumType, index) =>
                                                        new EnumDescriptor(enumType, this, null, index));

      services = DescriptorUtil.ConvertAndMakeReadOnly(proto.ServiceList,
                                                       (service, index) => new ServiceDescriptor(service, this, index));

      extensions = DescriptorUtil.ConvertAndMakeReadOnly(proto.ExtensionList,
                                                         (field, index) =>
                                                         new FieldDescriptor(field, this, null, index, true));
    }


    /// <summary>
    /// Allows a file descriptor to be configured with a set of external options, e.g. from the
    /// command-line arguments to protogen.
    /// </summary>
    internal void ConfigureWithDefaultOptions(CSharpFileOptions options) {
      csharpFileOptions = BuildOrFakeWithDefaultOptions(options);
    }

    private CSharpFileOptions BuildOrFakeWithDefaultOptions(CSharpFileOptions defaultOptions) {
      // Fix for being able to relocate these files to any directory structure
      if (proto.Package == "google.protobuf") {
        string filename = Path.GetFileName(proto.Name);
        // TODO(jonskeet): Check if we could use FileDescriptorProto.Descriptor.Name - interesting bootstrap issues)
        if (filename == "descriptor.proto") {
          return new CSharpFileOptions.Builder {
            Namespace = "Google.ProtocolBuffers.DescriptorProtos",
            UmbrellaClassname = "DescriptorProtoFile",
            NestClasses = false,
            MultipleFiles = false,
            PublicClasses = true,
            OutputDirectory = defaultOptions.OutputDirectory,
            IgnoreGoogleProtobuf = defaultOptions.IgnoreGoogleProtobuf
          }.Build();
        }
        if (filename == "csharp_options.proto") {
          return new CSharpFileOptions.Builder {
            Namespace = "Google.ProtocolBuffers.DescriptorProtos",
            UmbrellaClassname = "CSharpOptions",
            NestClasses = false,
            MultipleFiles = false,
            PublicClasses = true,
            OutputDirectory = defaultOptions.OutputDirectory,
            IgnoreGoogleProtobuf = defaultOptions.IgnoreGoogleProtobuf
          }.Build();
        }
      }
      CSharpFileOptions.Builder builder = defaultOptions.ToBuilder();
      if (proto.Options.HasExtension(DescriptorProtos.CSharpOptions.CSharpFileOptions)) {
        builder.MergeFrom(proto.Options.GetExtension(DescriptorProtos.CSharpOptions.CSharpFileOptions));
      }
      if (!builder.HasNamespace) {
        builder.Namespace = Package;
      }
      if (!builder.HasUmbrellaClassname) {
        int lastSlash = Name.LastIndexOf('/');
        string baseName = Name.Substring(lastSlash + 1);
        builder.UmbrellaClassname = NameHelpers.UnderscoresToPascalCase(NameHelpers.StripProto(baseName));
      }

      // Auto-fix for name collision by placing umbrella class into a new namespace.  This
      // still won't fix the collisions with nesting enabled; however, you have to turn that on explicitly anyway.
      if (!builder.NestClasses && !builder.HasUmbrellaNamespace) {
        bool collision = false;
        foreach (IDescriptor d in MessageTypes) {
          collision |= d.Name == builder.UmbrellaClassname;
        }
        foreach (IDescriptor d in Services) {
          collision |= d.Name == builder.UmbrellaClassname;
        }
        foreach (IDescriptor d in EnumTypes) {
          collision |= d.Name == builder.UmbrellaClassname;
        }
        if (collision) {
          builder.UmbrellaNamespace = "Proto";
        }
      }

      return builder.Build();
    }

    /// <value>
    /// The descriptor in its protocol message representation.
    /// </value>
    public FileDescriptorProto Proto {
      get { return proto; }
    }

    /// <value>
    /// The <see cref="DescriptorProtos.FileOptions" /> defined in <c>descriptor.proto</c>.
    /// </value>
    public FileOptions Options {
      get { return proto.Options; }
    }

    /// <summary>
    /// Returns the C#-specific options for this file descriptor. This will always be
    /// completely filled in.
    /// </summary>
    public CSharpFileOptions CSharpOptions {
      get {
        lock (optionsLock) {
          if (csharpFileOptions == null) {
            csharpFileOptions = BuildOrFakeWithDefaultOptions(CSharpFileOptions.DefaultInstance);
          }
        }
        return csharpFileOptions;
      }
    }

    /// <value>
    /// The file name.
    /// </value>
    public string Name {
      get { return proto.Name; }
    }

    /// <summary>
    /// The package as declared in the .proto file. This may or may not
    /// be equivalent to the .NET namespace of the generated classes.
    /// </summary>
    public string Package {
      get { return proto.Package; }
    }

    /// <value>
    /// Unmodifiable list of top-level message types declared in this file.
    /// </value>
    public IList<MessageDescriptor> MessageTypes {
      get { return messageTypes; }
    }

    /// <value>
    /// Unmodifiable list of top-level enum types declared in this file.
    /// </value>
    public IList<EnumDescriptor> EnumTypes {
      get { return enumTypes; }
    }

    /// <value>
    /// Unmodifiable list of top-level services declared in this file.
    /// </value>
    public IList<ServiceDescriptor> Services {
      get { return services; }
    }

    /// <value>
    /// Unmodifiable list of top-level extensions declared in this file.
    /// </value>
    public IList<FieldDescriptor> Extensions {
      get { return extensions; }
    }

    /// <value>
    /// Unmodifiable list of this file's dependencies (imports).
    /// </value>
    public IList<FileDescriptor> Dependencies {
      get { return dependencies; }
    }

    /// <value>
    /// Implementation of IDescriptor.FullName - just returns the same as Name.
    /// </value>
    string IDescriptor.FullName {
      get { return Name; }
    }

    /// <value>
    /// Implementation of IDescriptor.File - just returns this descriptor.
    /// </value>
    FileDescriptor IDescriptor.File {
      get { return this; }
    }

    /// <value>
    /// Protocol buffer describing this descriptor.
    /// </value>
    IMessage IDescriptor.Proto {
      get { return Proto; }
    }

    /// <value>
    /// Pool containing symbol descriptors.
    /// </value>
    internal DescriptorPool DescriptorPool {
      get { return pool; }
    }

    /// <summary>
    /// Finds a type (message, enum, service or extension) in the file by name. Does not find nested types.
    /// </summary>
    /// <param name="name">The unqualified type name to look for.</param>
    /// <typeparam name="T">The type of descriptor to look for (or ITypeDescriptor for any)</typeparam>
    /// <returns>The type's descriptor, or null if not found.</returns>
    public T FindTypeByName<T>(String name)
      where T : class, IDescriptor {
      // Don't allow looking up nested types.  This will make optimization
      // easier later.
      if (name.IndexOf('.') != -1) {
        return null;
      }
      if (Package.Length > 0) {
        name = Package + "." + name;
      }
      T result = pool.FindSymbol<T>(name);
      if (result != null && result.File == this) {
        return result;
      }
      return null;
    }

    /// <summary>
    /// Builds a FileDescriptor from its protocol buffer representation.
    /// </summary>
    /// <param name="proto">The protocol message form of the FileDescriptor.</param>
    /// <param name="dependencies">FileDescriptors corresponding to all of the
    /// file's dependencies, in the exact order listed in the .proto file. May be null,
    /// in which case it is treated as an empty array.</param>
    /// <exception cref="DescriptorValidationException">If <paramref name="proto"/> is not
    /// a valid descriptor. This can occur for a number of reasons, such as a field
    /// having an undefined type or because two messages were defined with the same name.</exception>
    public static FileDescriptor BuildFrom(FileDescriptorProto proto, FileDescriptor[] dependencies) {
      // Building descriptors involves two steps: translating and linking.
      // In the translation step (implemented by FileDescriptor's
      // constructor), we build an object tree mirroring the
      // FileDescriptorProto's tree and put all of the descriptors into the
      // DescriptorPool's lookup tables.  In the linking step, we look up all
      // type references in the DescriptorPool, so that, for example, a
      // FieldDescriptor for an embedded message contains a pointer directly
      // to the Descriptor for that message's type.  We also detect undefined
      // types in the linking step.
      if (dependencies == null) {
        dependencies = new FileDescriptor[0];
      }

      DescriptorPool pool = new DescriptorPool(dependencies);
      FileDescriptor result = new FileDescriptor(proto, dependencies, pool);

      if (dependencies.Length != proto.DependencyCount) {
        throw new DescriptorValidationException(result,
                                                "Dependencies passed to FileDescriptor.BuildFrom() don't match " +
                                                "those listed in the FileDescriptorProto.");
      }
      for (int i = 0; i < proto.DependencyCount; i++) {
        if (dependencies[i].Name != proto.DependencyList[i]) {
          throw new DescriptorValidationException(result,
                                                  "Dependencies passed to FileDescriptor.BuildFrom() don't match " +
                                                  "those listed in the FileDescriptorProto.");
        }
      }

      result.CrossLink();
      return result;
    }

    private void CrossLink() {
      foreach (MessageDescriptor message in messageTypes) {
        message.CrossLink();
      }

      foreach (ServiceDescriptor service in services) {
        service.CrossLink();
      }

      foreach (FieldDescriptor extension in extensions) {
        extension.CrossLink();
      }

      foreach (MessageDescriptor message in messageTypes) {
        message.CheckRequiredFields();
      }
    }

    /// <summary>
    /// This method is to be called by generated code only.  It is equivalent
    /// to BuildFrom except that the FileDescriptorProto is encoded in
    /// protocol buffer wire format. This overload is maintained for backward
    /// compatibility with source code generated before the custom options were available
    /// (and working).
    /// </summary>
    public static FileDescriptor InternalBuildGeneratedFileFrom(byte[] descriptorData, FileDescriptor[] dependencies) {
      return InternalBuildGeneratedFileFrom(descriptorData, dependencies, x => null);
    }

    /// <summary>
    /// This delegate should be used by generated code only. When calling
    /// FileDescriptor.InternalBuildGeneratedFileFrom, the caller can provide
    /// a callback which assigns the global variables defined in the generated code
    /// which point at parts of the FileDescriptor. The callback returns an
    /// Extension Registry which contains any extensions which might be used in
    /// the descriptor - that is, extensions of the various "Options" messages defined
    /// in descriptor.proto. The callback may also return null to indicate that
    /// no extensions are used in the descriptor.
    /// </summary>
    /// <param name="descriptor"></param>
    /// <returns></returns>
    public delegate ExtensionRegistry InternalDescriptorAssigner(FileDescriptor descriptor);

    public static FileDescriptor InternalBuildGeneratedFileFrom(byte[] descriptorData,
                                                                FileDescriptor[] dependencies,
                                                                InternalDescriptorAssigner descriptorAssigner) {
      FileDescriptorProto proto;
      try {
        proto = FileDescriptorProto.ParseFrom(descriptorData);
      }
      catch (InvalidProtocolBufferException e) {
        throw new ArgumentException("Failed to parse protocol buffer descriptor for generated code.", e);
      }

      FileDescriptor result;
      try {
        result = BuildFrom(proto, dependencies);
      }
      catch (DescriptorValidationException e) {
        throw new ArgumentException("Invalid embedded descriptor for \"" + proto.Name + "\".", e);
      }

      ExtensionRegistry registry = descriptorAssigner(result);

      if (registry != null) {
        // We must re-parse the proto using the registry.
        try {
          proto = FileDescriptorProto.ParseFrom(descriptorData, registry);
        }
        catch (InvalidProtocolBufferException e) {
          throw new ArgumentException("Failed to parse protocol buffer descriptor for generated code.", e);
        }

        result.ReplaceProto(proto);
      }
      return result;
    }

    /// <summary>
    /// Replace our FileDescriptorProto with the given one, which is
    /// identical except that it might contain extensions that weren't present
    /// in the original. This method is needed for bootstrapping when a file
    /// defines custom options. The options may be defined in the file itself,
    /// so we can't actually parse them until we've constructed the descriptors,
    /// but to construct the decsriptors we have to have parsed the descriptor
    /// protos. So, we have to parse the descriptor protos a second time after
    /// constructing the descriptors.
    /// </summary>
    private void ReplaceProto(FileDescriptorProto newProto) {
      proto = newProto;

      for (int i = 0; i < messageTypes.Count; i++) {
        messageTypes[i].ReplaceProto(proto.GetMessageType(i));
      }

      for (int i = 0; i < enumTypes.Count; i++) {
        enumTypes[i].ReplaceProto(proto.GetEnumType(i));
      }

      for (int i = 0; i < services.Count; i++) {
        services[i].ReplaceProto(proto.GetService(i));
      }

      for (int i = 0; i < extensions.Count; i++) {
        extensions[i].ReplaceProto(proto.GetExtension(i));
      }
    }
  }
}